In a computer network, route convergence is generally the process of agreement by routers on optimal routes. When a network event causes routes to fail or become available, routers distribute routing update messages that permeate throughout the computer network, which causes the routes to recalculate and agree on optimal routes.
For wide area network connectivity, many enterprise networks use a Layer 2 multipoint Ethernet service from a service provider for inter-site connectivity and deploy customer edge devices for inter-site routing. For route convergence, Border Gateway Protocol (BGP)/Interior Gateway Protocol (IGP) Hello timers may be used to detect connectivity failures between customer edge devices. The problem with this approach is that the use of Hello timers places a heavy processing burden on the customer edge devices. Each customer edge device may also run a Bidirectional Forwarding Detection (BFD) protocol session with every other customer edge device to detect connectivity failures. However, the use of BFD sessions requires excessive message generation, which also places a burden on the customer edge devices and utilizes network bandwidth. Route failures can also be detected by monitoring a line-protocol state on a user-network interface directly connected to the service provider edge device, but it cannot be used to detect connectivity failures that are deeper within the service provider's network.